09 September 2008

Elegant Gas Compression Technology

Both a matter of some fundamental science and a particularly elegant technology. The technology is the Australian Aboriginal firestarter. What makes it elegant is that it is simple, easy to use, makes a good demonstration of a physical principle, and is extremely obvious -- in retrospect. The way it works is that you take an airtight tube with a snugly fitting piston in it. Put the tube, with the piston at the top end, over some dry tinder. Then slam down the piston, while holding the tube hard against the ground.

The principle is that as you compress a gas, while keeping it insulated from the surroundings, it heats up. Compress it enough, and you get to the ignition point of your tinder. As far as I've seen, after doing a little looking when I saw the description of the Australian Aboriginal firestarter, they are the first people by some thousands of years to make use of the technology. Brilliant! elegant!

The next technology to make use of the principle, as far as I know, is the Diesel engine, late 1800s.

For our climate concerns, we don't deal with such extreme or rapid compressions. But the principle holds: If we take a blob of air, insulated from the surroundings and increase the pressure on it (because we're pulling it from lower pressure part of the atmosphere to higher), it warms up. The converse is also true -- if we decrease the pressure (by moving to a higher (lower pressure) part of the atmoshere), then the gas cools off.

This is another part of dealing with potential temperatures -- we'll get rigorous about by just how much the air warms or cools. But that's another note.

If you have other examples of technologies or cultures using air compression heating between the firestarter and Diesel engine, please do mention them here or by email to me at plutarchspam at aim dot net. (It's a valid address, the 'spam' in it is part of the name. You could also use the bobg at radix dot net that is in my profile, but I get so much unfiltered spam there that chances are good I'll miss your note.)


andrewt said...

Fire piston are fascinating but not an Australian technology - Wikipedia suggests SE Asia.

Anonymous said...

The fire piston is COOL! Or perhaps I should say, HOT!

Anonymous said...

Climate change wars lesson: Just because someone says something on a blog, doesn't mean its true.

If they can't back up the claim with references or evidence, it doesn't hurt to be suspicious.

Wikipedia says SE Asia and Pacific Islands, so that could conceivably also mean Australia. But a quick google search revealed nothing...

Robert Grumbine said...

Less quick searches by others showed Australia as well as SE Asia and Pacific islands the last time I mentioned this (some years ago in a different venue).

But the main points of the original remain, regardless of who the inventor(s) was/were -- compressing gases heat them, and this was a brilliant invention.

Still, of course, it'd be nice to have everything correct! Now, I actually do have a good source on this. Unfortunately, I'm a lot better at remembering results than sources. So all I'm sure of is that it's from one of my history of technology books that I've read in the last 10-15 years. Between library disarray and there being quite a few such books ... can't share that source.

And that leaves us with what Michael was noting -- if it can't be backed up with a source, it's less reliable for others. Several other issues, too, and I'll take them up in a post now.

Anonymous said...

Serendipity strikes.

After I read your article, the Arbor Scientific 2009 catalogue arrived and I spotted their Fire Syringe. Arborsci has a video clip of it in action


Could be a nice classroom demo.